Reaktionsabläufen

Reaktionsabläufe describe the sequence of elementary steps that make up an overall chemical reaction. A chemical reaction, as observed in a laboratory, is rarely a single event. Instead, it proceeds through a series of intermediate molecular transformations. Each of these individual steps is called an elementary reaction. The collection of these elementary reactions, in their specific order, constitutes the reaction mechanism or reaction pathway.

Understanding the reaction mechanism is crucial for comprehending the kinetics and thermodynamics of a chemical process. It helps explain why a reaction occurs at a certain rate, what factors influence that rate, and why specific products are formed. Some elementary steps might be fast, while others are slow. The slowest elementary step in a reaction mechanism is often referred to as the rate-determining step, as it limits the overall speed of the reaction.

Various experimental techniques can be employed to elucidate reaction mechanisms, including studying the effect of concentration and temperature on reaction rates, identifying transient intermediates, and using isotopic labeling. Computational chemistry also plays a significant role in proposing and validating proposed reaction pathways. For instance, in the Haber-Bosch process for ammonia synthesis, the overall reaction N₂ + 3H₂ → 2NH₃ occurs through a complex series of adsorption, dissociation, and recombination steps on a catalyst surface. The detailed understanding of such reaction sequences is fundamental to chemical engineering and the design of efficient chemical processes.